Celal Mohan Ögün

Modelling of indium(I) iodide-argon low pressure plasma

A new collisional-radiative model for a mercury-free low pressure plasma based on an indium(I) iodide-argon system is presented. The electron impact cross sections and rate coefficients for ionization, excitation and dissociation, as well as de-excitation, three-body recombination and dissociative recombination, of studied fillings have been calculated. Additionally, the coefficients for free and ambipolar diffusion were determined. The rate balance equations for individual generation and loss processes have been created. Densities of ions, electrons and neutral particles (ground or metastable state) are presented as a function of electron temperature for varied lamp parameters, such as argon buffer gas pressure and cold spot temperature (coldest point of discharge vessel). With the help of the presented model, the line emission coefficients of essential emission lines of indium for given electron temperatures and densities can be predicted.

Characteristics of a surfatron-produced atmospheric-pressure plasma jet at low plasma temperatures

Summary form only given. The need of Atmospheric-Pressure Plasma is becoming increasingly important in several application fields like surface treatment for coating industry or microbicidal treatment. Due to a lot of investigation the discharge at atmospheric pressure has developed a wide range of applications over the last years, such as microbial decontamination. One of the possibly most interesting characteristics of an atmospheric pressure plasma is that it can fill the gap between low pressure and high pressure plasmas as it enables likewise high-temperature plasmas with a thermal equilibrium and low-temperature plasmas with high-energy electrons.High temperature plasmas can be deployed for the disinfection of non-organic materials compatible with these high temperatures, like titanium implants. Surface wave driven plasmas allow high electron and low plasma temperatures at low injected powers. A low plasma temperature enables to also treat materials sensitive to high temperatures or furthermore even the human skin. An optimized Surface-design developed at the Light Technology Institute of the Karlsruhe Institute of Technology enables higher field strengths and by that an stable ionization of the working gas at lower induced powers. Besides the power the effective temperature of the plasma strongly depends on the gas flow rate. This research focuses on the characterization of plasmas with an effective plasma temperature below 50°C. An extension of the detailed understanding of all processes within an Atmospheric-Pressure Plasma Jet at this low temperatures is the main object of this research. In this work all relevant plasma parameters such as the plasma temperature, electron temperature, plasma density and its UV- and ViS-spectrum are studied. The consequent characteristics of the cold plasma jet is then evaluated concerning their possible fields of application.

Diagnostics of surface wave driven low pressure plasmas based on indium monoiodide-argon system

Indium monoiodide is proposed as a suitable alternative to hazardous mercury, i.e. the emitting component inside the compact fluorescent lamps (CFL), with comparable luminous efficacy. Indium monoiodide-argon low pressure lamps are electrodelessly driven with surface waves, which are launched and coupled into the lamp by the ‘surfatron’, a microwave coupler optimized for an efficient operation at a frequency of 2.45 GHz. A non intrusive diagnostic method based on spatially resolved optical emission spectroscopy is employed to characterize the plasma parameters. The line emission coefficients of the plasma are derived by means of Abel’s inversion from the measured spectral radiance data. The characteristic plasma parameters, e.g. electron temperature and density are determined by comparing the experimentally obtained line emission coefficients with simulated ones from a collisional-radiative model. Additionally, a method to determine the absolute plasma efficiency via irradiance measurements without any goniometric setup is presented. In this way, the relationship between the plasma efficiency and the plasma parameters can be investigated systematically for different operating configurations, e.g. electrical input power, buffer gas pressure and cold spot temperature. The performance of indium monoiodide-argon plasma is compared with that of conventional CFLs.

Modeling and characterization of an indium(I)iodide-argon low pressure lamp

Summary form only given. Compact fluorescent lamps are broadly used for general lighting applications [1], yet they still struggle with acceptance problems, since they contain hazardous mercury as an elementary component. The presented work is a part of a project to substitute mercury with non-hazardous materials. For the efficiency increase and further improvement of the lamp, the determination of the plasma parameters is of utmost importance. For this purpose, the mercury free discharge based on indium(I)iodide-argon system is modeled on the basis of an extended corona model. The electron impact ionization and excitation cross sections of atomic components were calculated by means of Gryzinski method [2], while the method from [3] was used for calculation of ionization and dissociation cross sections of molecular indium(I)iodide. Ambipolar and free diffusion coefficients were determined by Chapman-Enskog-theory [4]. The rate equations for individual generation and loss processes were developed. Computational tools to solve the rate equations were programmed with MATLAB. With the help of this model, the plasma parameters like electron temperature, electron density and the line emission coefficients can be predicted at any given lamp configuration like puffer gas pressure or cold spot temperature.

Characterization of the starting and stabilization processes inside an electrodeless low pressure mercury lamp driven with pulsed mode surface waves

Summary form only given. The low pressure mercury lamp is dominating the lighting market for decades. In these lamps the electrode loss is one the dominant factors that limit the efficacy of the lamp. Thus by removing the electrodes and sustaining the discharge with surface waves, the efficacy, which the lamp ideally delivers, can be obtained. In addition, with electrodes associated failure mechanism like the loss of emission materials or the darkening of the lamp bulb will also be eliminated. In this way it is possible to increase the efficacy as well as the lifetime of the lamp.

Operating of electrode less, indium iodide based high intensity discharge lamps within the use of plasma guided microwaves

Summary form only given. The increase of the efficacy as well as the lifetime of high intensity discharge lamps (HID lamps) is the object of the present research. One of the main limits is the thermal loss due to the lamps electrodes. This reduces the lamps efficacy. Furthermore, corrosion of the electrodes is the main failure criteria and limits the lifetime of the lamp. One possible solution for this is the plasma stimulation by plasma guided microwaves. In this way both of the effects can be prevented by heating the discharge without electrodes.